IN-VITRO SELECTION OF RNA-BASED IRREVERSIBLE INHIBITORS OF HUMAN NEUTROPHIL ELASTASE

Introduction: We describe a new approach to drug discovery which joins the technologies of medicinal and combinatorial chemistry, allowing s election of the most active variant of a lead compound from a large (> 10(12)) Pool. A small-molecule covalent inhibitor of elastase was coup led to a randomized pool of RNA, and this assembly was iteratively sel ected for oligonucleotide sequences that promote the covalent reaction of the inhibitor with the human neutrophil elastase (hNE) active site . Results: Incorporation of the covalent inhibitor into the randomized pool increases the second-order rate of inactivation of hNE by simila r to 15-fold; sequences selected from this pool show an additional sim ilar to 20-fold increase in activity The relative rate of cross-reacti on with another serine protease, cathepsin G, was reduced >100-fold. L ow doses of the inhibitor were found to prevent lung damage inflicted by human neutrophils in an isolated rat lung model of acute: respirato ry distress syndrome (ARDS). Conclusions: This result supports the hyp othesis that neutrophil elastase is a significant effector of inflamma tory disease. More generally, our findings demonstrate that blending s mall molecules into combinatorial libraries is a feasible method of dr ug discovery.